SCEC Award Number 13123 View PDF
Proposal Category Collaborative Proposal (Integration and Theory)
Proposal Title The role of pore-fluid pressure on fault behavior at the base of the seismogenic zone
Investigator(s)
Name Organization
Greg Hirth Brown University Nick Beeler United States Geological Survey
Other Participants Graduate Student Taka Kanaya (second year)
SCEC Priorities 1, 3, 5 SCEC Groups FARM, SDOT, Geodesy
Report Due Date 03/15/2014 Date Report Submitted 11/17/2015
Project Abstract
 To characterize stress and deformation style at the base of the seismogenic zone we developed a conceptual model and investigated how the mechanical properties of fluid-rock systems respond to variations in temperature and strain rate. The role of fluids on the processes responsible for the brittle-ductile transition in quartz-rich rocks has not been explored at experimental conditions where the kinetic competition between microcracking and viscous flow is similar to that expected in the Earth. Our initial analysis of this competition suggests that the effective pressure law for sliding friction should not work as efficiently near the brittle-ductile transition (BDT) as it does at shallow conditions (Hirth and Beeler, 2014; Beeler et al., 2015). Our experiments demonstrate a temperature and strain rate dependence of deformation during semi-brittle flow of quartzite. The resulting “flow law” indicates deformation is rate limited by sub-critical crack growth, potentially in response to emission of dislocation at crack tips. Our results also provide a quantification of the role of water on the strength of quartzites in the semi- brittle flow regime.
Intellectual Merit N/A
Broader Impacts The results of our project are being presented during lectures for classes and during seminars at other labs, universities and meetings.
Exemplary Figure N/A